Imidazolinones or imidazolones are a family of heterocyclic compounds, the parents of which have the formula OC(NH)<sub>2</sub>(CH)<sub>2</sub>. Two isomers are possible, depending on the location of the carbonyl (CO) group. The NH groups are nonadjacent. A common route to imidazol-2-ones involves condensation of ureas and acyloins. Some are of interest in the pharmaceuticals. 4-Imidazolones arise from the condensation of amidines with 1,2-dicarbonyls such as glyoxal.
Imidazolinone herbicides work by inhitibing acetolactate synthase and belong to the HRAC class of . These herbicides include imazapic, imazamethabenz-methyl, imazamox, imazapyr, imazaquin and imazethapyr.